Long-Half-Life 89Zr-Labeled Radiotracers Can Guide Percutaneous Biopsy Within the PET/CT Suite Without Reinjection of Radiotracer

Augmenting CT-Guided Bone Biopsies Using 18F-FDG PET/CT Guidance

Computer tomography (CT)-guided percutaneous core biopsies are currently the gold standard in diagnostic procedures for patients with bone lesions of unknown kind. CT-guided biopsies can lead to misdiagnosis or repetition of biopsies in case of small or heterogeneous lesions. We hypothesize that molecular image guidance could be used to optimize the biopsy strategy, by supporting the detection of heterogeneous lesions or lesions without radiographic substrate. To evaluate this hypothesis, we investigated if and how the addition of 2-deoxy-2-18F-fluoro-D-glucose-positron emission tomography (18F-FDG-PET)/CT could augment routine CT-guided bone biopsies. To this end, 106 patients who underwent a CT-guided bone biopsy between April 2019 and April 2020, obtained from either a vertebral or peripheral bone, were included. Patients were divided into 2 groups: 36 patients received an 18F-FDG-PET/CT scan prior to their CT-guided bone biopsy (PET group), while 70 patients only had a morphological CT scan (CT group). Histopathology was used to categorize biopsies into five subgroups (inconclusive, benign, malignant or infectious disease, or normal tissue). In the PET group, the number of conclusive biopsies was significantly higher compared to the CT group (N = 33/36 (92%) versus N = 53/70 (76%); p < 0.05). Furthermore, the number of first-try biopsies was lower in the PET group compared to the CT group (1.9 vs. 2.54, p = 0.051). In conclusion, 18F-FDG-PET/CT imaging significantly increased the success rate of first-try CT-guided bone biopsies by showing less inconclusive biopsies and misdiagnosis.

Long-Term Tumor-Targeting Effect of E. coli as a Drug Delivery System

To overcome the limitations of current nano/micro-scale drug delivery systems, an Escherichia coli (E. coli)-based drug delivery system could be a potential alternative, and an effective tumor-targeting delivery system can be developed by attempting to perform chemical binding to the primary amine group of a cell membrane protein. In addition, positron emission tomography (PET) is a representative non-invasive imaging technology and is actively used in the field of drug delivery along with radioisotopes capable of long-term tracking, such as zirconium-89 (89Zr). The membrane proteins were labeled with 89Zr using chelate (DFO), and not only was the long-term biodistribution in tumors and major organs evaluated in the body, but the labeling stability of 89Zr conjugated to the membrane proteins was also evaluated through continuous tracking. E. coli accumulated at high levels in the tumor within 5 min (initial time) after tail intravenous injection, and when observed after 6 days, 89Zr-DFO on the surface of E. coli was found to be stable for a long period of time in the body. In this study, we demonstrated the long-term biodistribution and tumor-targeting effect of an E. coli-based drug delivery system and verified the in vivo stability of radioisotopes labeled on the surface of E. coli.

Current Status of Radiolabeled Monoclonal Antibodies Targeting PSMA for Imaging and Therapy

Prostate cancer (PCa) is one of the most prevalent cancer diagnoses among men in the United States and in several other developed countries. The prostate specific membrane antigen (PSMA) has been recognized as a promising molecular target in PCa, which has led to the development of specific radionuclide-based tracers for imaging and radiopharmaceuticals for PSMA targeted therapy. These compounds range from small molecule ligands to monoclonal antibodies (mAbs). Monoclonal antibodies play a crucial role in targeting cancer cell-specific antigens with a high degree of specificity while minimizing side effects to normal cells. The same mAb can often be labeled in different ways, such as with radionuclides suitable for imaging with Positron Emission Tomography (β+ positrons), Gamma Camera Scintigraphy (γ photons), or radiotherapy (β- electrons, α-emitters, or Auger electrons). Accordingly, the use of radionuclide-based PSMA-targeting compounds in molecular imaging and therapeutic applications has significantly grown in recent years. In this article, we will highlight the latest developments and prospects of radiolabeled mAbs that target PSMA for the detection and treatment of prostate cancer.

Multiplexed imaging in oncology

In oncology, technologies for clinical molecular imaging are used to diagnose patients, establish the efficacy of treatments and monitor the recurrence of disease. Multiplexed methods increase the number of disease-specific biomarkers that can be detected simultaneously, such as the overexpression of oncogenic proteins, aberrant metabolite uptake and anomalous blood perfusion. The quantitative localization of each biomarker could considerably increase the specificity and the accuracy of technologies for clinical molecular imaging to facilitate granular diagnoses, patient stratification and earlier assessments of the responses to administered therapeutics. In this Review, we discuss established techniques for multiplexed imaging and the most promising emerging multiplexing technologies applied to the imaging of isolated tissues and cells and to non-invasive whole-body imaging. We also highlight advances in radiology that have been made possible by multiplexed imaging.

89Zr-PET imaging in humans: a systematic review

Purpose

The remarkable amount of preclinical data achieved on 89Zr-PET imaging led to a significant clinical translation, concerning mainly immuno-PET applications. The aim of this systematic review is to provide a complete overview on clinical applications of 89Zr-PET imaging, using a systematic approach to identify and collect published studies performed in humans, sorted by field of application and specific disease subsections.

Methods

A systematic literature search of articles suiting the inclusion criteria was conducted on Pubmed, Scopus, Central, and Web Of Science databases, including papers published from January 1967 to November 2020. Eligible studies had to be performed on humans through PET imaging with 89Zr-labeled compounds. The methodological quality was assessed through the Quality Assessment of Diagnostic accuracy Studies-2 tool.

Results

A total of 821 articles were screened. 74 studies performed on humans were assessed for eligibility with the exclusion of further 18, thus 56 articles were ultimately selected for the qualitative analysis.

Conclusions

89Zr has shown to be a powerful PET-imaging tool, in particular for radiolabeling antibodies in order to study antigen expression, biodistribution, anticancer treatment planning and follow-up. Other than oncologic applications, 89Zr-radiolabeled antibodies have been proposed for use in inflammatory and autoimmune disorders with interesting results. 89Zr-labeled nanoparticles represent groundbreaking radiopharmaceuticals with potential huge fields of application. To evaluate the clinical usefulness of 89Zr PET-imaging in different conditions and in real-world settings, and to widen its use in clinical practice, further translation of preclinical to clinical data is needed.

Practice and prospects for PET/CT guided interventions

During the past 10 years, performing real-time molecular imaging with positron emission tomography (PET) in combination with computed tomography (CT) during interventional procedures has undergone rapid development. Keeping in mind the interest of the nuclear medicine readers, an update is provided of the current workflows using real-time PET/CT in percutaneous biopsies and tumor ablations. The clinical utility of PET/CT guided biopsies in cancer patients with lung, liver, lymphoma, and bone tumors are reviewed. Several technological developments, including the introduction of new PET tracers and robotic arms as well as opportunities provided through acquiring radioactive biopsy specimens are briefly reviewed.

Polyazamacrocycle Ligands Facilitate 89Zr Radiochemistry and Yield 89Zr Complexes with Remarkable Stability

Over the last three decades, the chemistry of zirconium has facilitated antibody development and the clinical management of disease in the precision medicine era. Scientists have harnessed its reactivity, coordination chemistry, and nuclear chemistry to develop antibody-based radiopharmaceuticals incorporating zirconium-89 (⁸⁹Zr: t_1/2 = 78.4 h, β⁺: 22.8%, E_β+max = 901 keV; EC: 77%, E_γ = 909 keV) to improve disease detection, identify patients for individualized therapeutic interventions. and monitor their response to those interventions. However, release of the ⁸⁹Zr⁴⁺ ion from the radiopharmaceutical remains a concern, since it may confound the interpretation of clinical imaging data, negatively affect dosimetric calculations, and hinder treatment planning. In this report, we relate our novel observations involving the use of polyazamacrocycles as zirconium-89 chelators. We describe the synthesis and complete characterization of zirconium 2,2',2″,2‴-(1,4,7,10-tetraazacyclotridecane-1,4,7,10-tetrayl)tetraacetic acid (Zr-TRITA), zirconium 3,6,9,15-Tetraazabicyclo[9.3.1] pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (Zr-PCTA), and zirconium 2,2',2″-(1,4,7-triazacyclononane-1,4,7-triyl)triacetic acid (Zr-NOTA). In addition, we elucidate the solid-state structure of each complex using single-crystal X-ray diffraction analysis. Finally, we found that [⁸⁹Zr]Zr-PCTA and [⁸⁹Zr]Zr-NOTA demonstrate excellent stability in vitro and in vivo and provide a rationale for these observations. These innovative findings have the potential to guide the development of safer and more robust immuno-PET agents to improve precision medicine applications.

Current Perspectives on 89Zr-PET Imaging

⁸⁹Zr is an emerging radionuclide that plays an essential role in immuno-positron emission tomography (PET) imaging. The long half-life of ⁸⁹Zr (t_1/2 = 3.3 days) is favorable for evaluating the in vivo distribution of monoclonal antibodies. Thus, the use of ⁸⁹Zr is promising for monitoring antibody-based cancer therapies. Immuno-PET combines the sensitivity of PET with the specificity of antibodies. A number of studies have been conducted to investigate the feasibility of ⁸⁹Zr immuno-PET imaging for predicting the efficacy of radioimmunotherapy and antibody therapies, imaging target expression, detecting target-expressing tumors, and the monitoring of anti-cancer chemotherapies. In this review, we summarize the current status of PET imaging using ⁸⁹Zr in both preclinical and clinical studies by highlighting the use of immuno-PET for the targets of high clinical relevance. We also present ⁸⁹Zr-PET applications other than immuno-PET, such as nanoparticle imaging and cell tracking. Finally, we discuss the limitations and the ongoing research being performed to overcome the remaining hurdles.

Identification of HER2-Positive Metastases in Patients with HER2-Negative Primary Breast Cancer by Using HER2-targeted 89Zr-Pertuzumab PET/CT

Background Human epidermal growth factor receptor 2 (HER2)-targeted therapies are successful in patients with HER2-positive malignancies; however, spatial and temporal heterogeneity of HER2 expression may prevent identification of optimal patients for these therapies. Purpose To determine whether imaging with the HER2-targeted PET tracer zirconium 89 (⁸⁹Zr)-pertuzumab can depict HER2-positive metastases in women with HER2-negative primary breast cancer. Materials and Methods From January to June 2019, women with biopsy-proven HER2-negative primary breast cancer and biopsy-proven metastatic disease were enrolled in a prospective clinical trial (ClinicalTrials.gov NCT02286843) and underwent ⁸⁹Zr-pertuzumab PET/CT for noninvasive whole-biopsy evaluation of potential HER2-positive metastases. ⁸⁹Zr-pertuzumab-avid foci that were suspicious for HER2-positive metastases were tissue sampled and examined by pathologic analysis to document HER2 status. Results Twenty-four women (mean age, 55 years ± 11 [standard deviation]) with HER2-negative primary breast cancer were enrolled. Six women demonstrated foci at ⁸⁹Zr-pertuzumab PET/CT that were suspicious for HER2-positive disease. Of these six women, three had biopsy-proven HER2-positive metastases, two had pathologic findings that demonstrated HER2-negative disease, and one had a fine-needle aspirate with inconclusive results. Conclusion Human epidermal growth factor receptor 2 (HER2)-targeted imaging with zirconium 89-pertuzumab PET/CT was successful in detecting HER2-positive metastases in women with HER2-negative primary breast cancer. This demonstrates the ability of targeted imaging to identify patients for targeted therapies that might not otherwise be considered. © RSNA, 2020 Online supplemental material is available for this article. See the editorial by Mankoff and Pantel in this issue.

Positron emission tomography/computed tomography guided percutaneous biopsies of Ga-68 avid lesions using an automated robotic arm

PURPOSE

The purpose of this prospective study was to evaluate the feasibility of positron emission tomography/computed tomography (PET/CT)-guided biopsy of Ga-68 avid lesions using an automated robotic arm and determine the diagnostic yield of this technique.

MATERIAL AND METHODS

Patients who underwent Ga-68 labelled tracers imaging followed by PET/CT-guided biopsies of tracer-avid lesions were prospectively included. Biopsies were performed using a dedicated automated-robotic-arm assisted PET/CT-guided biopsy device on the same-day of diagnostic PET/CT-imaging. The tissue samples were retrieved after confirming the position of needle-tip in the target lesion. Procedure-related complications and radiation exposure of the interventionist were recorded. Histopathological reports were reviewed for diagnostic yield.

RESULTS

A total of 25 patients (19 men, six women) with a mean age of 50.8±17.3 (SD) years (range: 17-83 years) were included. The biopsies were performed after PET/CT using Ga-68 DOTANOC (n=16) or Ga-68 PSMA (n=8) and Ga-68 chemokine-analogue (n=1). The biopsy samples were obtained from the liver (n=9), bone (n=8), lymph-nodes (n=3), lung (n=1), pancreas (n=1), anterior mediastinal lesion (n=1), peritoneal-deposit (n=1) and thigh-lesion (n=1). No immediate or delayed procedure-related complications were documented in any patient. PET/CT-guided molecular sampling was technically successful in all the patients. Histopathology revealed malignancies in all the biopsied specimens without the need for repeat sampling or further invasive-diagnostic workup, with a diagnostic yield of 100%. The estimated absorbed-radiation dose was 566.7μSv/year for the interventionist.

CONCLUSION

PET/CT-guided molecular biopsy using Ga-68 labelled radiotracers is feasible and can be performed safely and accurately with a high-diagnostic yield. It is helpful in accurately staging the disease when tracer-avid isolated distant lesion evident on imaging and highly practical in patients with previous inconclusive sampling.

Clinical Potential of Human Epidermal Growth Factor Receptor 2 and Human Epidermal Growth Factor Receptor 3 Imaging in Breast Cancer

Increased expression of the human epidermal growth factor receptor (HER) protein family are targets in breast cancer for imaging and therapy. Imaging modalities targeting HER2 and HER3 can diagnose breast cancer with a specific, biologically relevant target. Repeat biopsies do not address heterogeneity intratumorally or between primary disease and metastasis. HER2- and HER3-targeted PET is an important tool to diagnose disease in breast cancer and evaluate response to targeted therapies. PET and single photon emission computed tomography with radiolabeled biomolecules can be used to detect and quantify specific targets, conferring a better understanding of the behavior and effectiveness of treatments.